Mini Medical School - Hematology
Grade level(s):Middle School (6-8), High School (9-12), Grade 7, Grade 8, Grade 9, Grade 10, Grade 11
Subjects(s):Biology/Life Science, Science Skills
Topic:Human Biology, Hematology, Physiology, Genetics
Blood is composed of red blood cells, white blood cells, platelets, and plasma.
Important functions of blood include oxygen transport, immunity, and clotting.
Methods to track changes (number and type of blood components) in blood (Complete Blood Count, Blood Smears) by comparing to Normal Samples
Many blood disorders can be diagnosed based on changes in the appearance or numbers/proportions of blood cell types.
Learning some genetic and enviromental components of blood disorders.
hematology, red blood cells (RBCs), white blood cells (WBCs), platelets (PLTs), plasma, clotting
What you need:
- For candy blood model: Red Hots (Walgreens), mini marshmallows, sprinkles, light corn syrup, 50 mL conical tubes or small cups, spoons/forks, disposable plates/bowls/cups, paper towels
- For diagnosis activity: normal and diseased blood slides or images, example Complete Blood Counts of normal and diseased patients, microscopes, scrubs or white coats (optional)
- Handouts: worksheet for blood model, take home reading assignment on blood and blood diseases, handouts on mock patients with patient history, CBC, and spaces to record observations and diagnosis
Students should work in pairs.
Classroom or lab equipped with microscopes.
Two classes, 50 minutes each.
- Intro, teach functions and components of blood (20 min)
- Build candy blood model (20 min)
- Wrap up and preview of day 2 (10 min)
- Intro, present patients and pass out handouts/materials (10 min)
- Students work in groups to diagnose patients (25 min)
- Groups report to class on diagnosis and rationale, discussion (10 min)
- Wrap up (5 min)
This is a two-class lesson plan. During the first class students are entered into a "mini-medical school" where they will learn about the functions and components of blood and make a candy model to reflect their relative proportions. At the end of the class, they graduate medical school as hematologists. The next day they will be presented with a mock patient with a blood disorder. In groups, they will attempt to diagnose the patient using blood smears, results of lab tests, and patient histories.
- understanding of proportions and measurement of appropriate volumes of liquids/solids
- use of microscopes to look at slides
Students will be able to:
- describe the functions of blood
- list the principle components of blood, their functions, and their relative abundance in blood
- give examples of blood diseases and their distinguishing features
- interpret data (blood smears and lab tests) and use critical thinking to develop an explanation (patient diagnosis) that fits the data
Hematology is the study of blood, the blood-forming organs, and blood diseases. Hematology includes the study of diagnosis, treatment, prognosis, and prevention of blood diseases.
Blood is a specialized bodily fluid in humans (and other animals) that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. The average human adult has more than 5 liters (6 quarts) of blood in his or her body. Blood is circulated around the body through blood vessels by the pumping action of the heart. Arterial blood carries oxygen from inhaled air to the tissues of the body, and venous blood carries carbon dioxide, a waste product of metabolism produced by cells, from the tissues to the lungs to be exhaled. Blood also delivers immune cells to fight infections and contains platelets that can form a plug in a damaged blood vessel to prevent blood loss.
Through the circulatory system, blood adapts to the body's needs. When you are exercising, the heart pumps harder and faster to provide more blood with oxygen to muscles. During an infection, the blood delivers more immune cells to the site of infection, where they accumulate to ward off harmful invaders.
All of these functions make blood a precious fluid. Each year in the USA, 30 million units of blood components are transfused to patients who need them. Blood is deemed so precious that is sometimes called red gold.
Blood contains cells, proteins, and sugars
If a test tube of blood is left to stand for half an hour, the blood separates into three layers as the denser components sink to the bottom of the tube and fluid remains at the top. The straw-colored fluid that forms the top layer is called plasma and forms about 55-60% of blood. The middle white layer is composed of white blood cells (WBCs) and platelets (PLTs), and the bottom red layer is the red blood cells (RBCs). These bottom two layers of cells form about 40-45% of the blood. All of the cells found in the blood come from bone marrow. They begin their life as stem cells, and they mature into three main types of cells— RBCs, WBCs, and PLTs.
Plasma is the liquid component of blood (55-60% volume), predominantly water. Plasma also contains dissolved nutrients (sugars, amino acids, vitamins, minerals), hormones, antibodies, clotting factors,and large proteins or complexes that act as carriers for substances that don't dissolve in water (fat, hormones, some vitamins). Plasma circulates nutrients throughout the body and picks up waste products for excretion (e.g. urea, carbon dioxide).
Red blood cells (RBCs) transport oxygen - Also known as erythrocytes, RBCs are the most common type of cells found in the blood. With each cubic millimeter of blood containing 4-6 million cells they make up about 40-45% of the total blood volume. RBCs are donut shaped (without the hole) and don't have nuclei. They are full of hemoglobin whi ch binds oxygen and to a lesser extent, carbon dioxide (most CO2 is transported dissolved in plasma or as bicarbonate). Hemoglobin is specially adapted to bind oxygen in the lungs and release it in tissue capillaries; the reverse is true for carbon dioxide. Hemoglobin gives blood its red color. Every second, 2-3 million RBCs are made in the bone marrow and circulate for about 120 days before being recycled in the spleen or liver. Below are photos of RBCs. The first one is a computer generated pictures and the second one shows RBCs as seen under a light microscope.
(Picture credit: left: http://singularityhub.com/wp-content/uploads/2008/08/red-blood-cells.bmp, right: http://27.media.tumblr.com/tumblr_ledvhxtRwX1qg1up7o1_500.gif)
If a patient has a low level of hemoglobin, a condition called anemia, they may appear pale because hemoglobin gives RBCs, and hence blood, their red color. They may also tire easily and feel short of breath because of the essential role of hemoglobin in transporting oxygen to the entire body from the lungs.
White blood cells (WBCs) - there are many types of WBCs with specialized functions, all involved in immunity and inflammation (0.5% of blood volume). Some WBCs only recognize a specific pathogen. If they find it, they proliferate and secrete products to kill the pathogen or recruit other immune cells to help. Other WBCs can respond to many classes of pathogens and also are involved in clearing debris and repairing tissues following a wound. WBCs are made in bone marrow and circulate in blood. They can also leave blood vessels to patrol tissues or respond to tissue damage or infection. Below are examples of WBCs as they can be seen under the microscope:
(Picture credit: http://www.scientificpsychic.com/mind/leukocytes0.jpg)
Platelets (PLTs) - fragments of cells that mediate clotting to prevent blood loss (0.5% blood volume). When platelets reach a site of blood vessel damage, they become activated and clump together to form a platelet plug that adheres to the damaged vessel wall to block blood loss. Platelets are formed in bone marrow by giant cells that stick their cytoplasmic extensions into blood vessels, which then break off to make platelets. If platelets are not activated to form blood clots they are removed by the spleen after about 9 days. In the blood smear below, the platelets are the small darker spots in between a large number of RBCs.
(Picture credit: http://img.medscape.com/pi/emed/ckb/hematology/197800-201722-4960.jpg)
Complete Blood Count
A complete blood count (CBC) is a simple blood test that is commonly ordered as part of a routine medical assessment. As the name suggests, it is a count of the different types of cells found in the blood. The test can diagnose and monitor many different diseases, such as anemia, infection, inflammatory diseases, and malignancy. Table 1 gives an example of CBC values
Table 1 – Components of the complete blood count (CBC)
Normal CBC Value
Amount in Just 1 mL of Blood
~7,000,000 in 1 mL
SF Bay Area
~5,000,000,000 in 1 mL
13 - 18 g/dL
45% to 52%
~300,000,000 in 1 mL
WBCs – the number of White Blood Cells; RBCs - the number of Red Blood Cells.; Hb - the total amount of Hemoglobin (Hb) in the blood; HCT - the amount of space RBCs take up in the blood also known as Hematocrit.; PLTs - number of platelets
The number of WBCs increases in infection and tumors
An increased number of WBCs is most commonly caused by infections. It may also be caused by WBC cancers, such as leukemia.
A decreased number of WBCs is caused by the bone marrow failing to produce WBCs or by an increased removal of WBCs from the circulation by a diseased liver or an overactive spleen. Bone marrow failure may be caused by toxins or by the normal bone marrow cells being replaced by tumor cells.
RBC count detects anemia
Anemia is a medical condition in which the red blood cell count or hemoglobin is less than normal. Anemia is caused through two basic pathways 1) by a decrease in production of red blood cell or hemoglobin, or 2) by a loss or destruction of red blood cells.
- Hematocrit is the percentage of RBCs in the total volume of blood: The hematocrit measures the fraction of the blood that is made up of RBCs. It reflects the combination of the total number of RBCs, and the volume that they occupy.
- Hemoglobin binds oxygen: Hemoglobin is the oxygen-carrying protein that is found within all RBCs. It picks up oxygen where it is abundant (the lungs) and drops off oxygen where it is needed around the body. Hemoglobin is also the pigment that gives RBCs their red color.
The number PLTs detects thrombocytopenia
Thrombocytopenia is a condition of low levels of platelets and carries an increased risk of bleeding. A high level of platelets (thrombocythemia) carries an increased risk of forming inappropriate blood clots. These clots could deprive essential organs such as the heart and brain, of their blood supply, causing heart attacks and strokes, respectively.
A peripheral blood smear is often used as a follow-up test to abnormal results on a complete blood count (CBC). Blood smears are generated by taking one drop of blood and smearing it across a glass slide then treating the smear with a stain (Wright-Giemsa) that makes the differences in the blood cells more apparent. It may be used to help diagnose and/or monitor numerous conditions that affect blood cell populations. A blood smear is often used to categorize and/or identify conditions that affect one or more types of blood cells and to monitor those undergoing treatment for these conditions. You can see all three blood components in a blood smear from a healthy person below.
(Picture credit: http://www.anatomybox.com/wp-content/uploads/2011/10/normal-human-blood-smear-600.jpg)
Genetic Disease of The Blood
RBC Disorders - Hemoglobinopathies
Hemoglobinopathies form a group of inherited diseases that are caused by mutations in hemoglobin. Sickle cell anemia is the most common of these and is attributable to a mutation that changes one of the amino acids in the hemoglobin, producing hemoglobin that is "fragile". Sickle patient RBCs tend to become distorted and "sickle" shaped on a blood smear. These deformed cells can block small blood vessels and damage the organs they are supplying. This can be very painful, and if not treated, a sickle cell crisis can be fatal.
Another inherited anemia that particularly affects individuals of Eastern descent is thalassemia. A fault in the production of either alpha or beta globin chains causes a range of symptoms, depending on how many copies of the alpha and beta genes are affected. Some individuals may be carriers of the disease and have no symptoms, whereas if all copies of the genes are lost, the disease is fatal. Patients with many hemoglobinopathies have reduced hemoglobin, appear pale, have enlarged spleens, and complain of being tired.
Sickle cell - 40x Thalassemia - 100x
(Picture credit: Left: http://www.pathology.vcu.edu/education/dental2/images/case1-1.jpg; Right: http://www.pathologystudent.com/wp-content/uploads/2009/07/thal1.jpg)
WBC Disorders - Leukemia
As do most cancers, leukemia strikes sporadically. Though hereditary influences or environmental exposures may contribute to risk, its occurrence is usually considered random. For some rare families, however, the disease is hereditary. In only a few dozen known cases, parents pass it to their offspring as a single gene. Leukemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts" (see pictures below). Leukemia is a broad term covering a spectrum of diseases.
(Picture credit: http://ctrgenpath.net/wp-content/uploads/2011/04/cml01.jpg)
PLT Disorders - Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood. Most thrombocytopenia cases do not have a genetic component; however, there are several genetic disorders that affect blood clotting. Von Willebrand disease (vWD) is the most common hereditary blood clotting disorder. It arises from a deficiency of von Willebrand factor, a protein that is required for platelet binding. Hemophilia is another group of hereditary genetic disorders that impair the body's ability to control blood clotting. Hemophilias are usually X chromosome disorders that are more likely to occur in males than females. The PLTs count in vWD or Haemophilia patients are usually unaffected. The picture below shows a healthy blood smear (top) and one from a patient with thrombocytopenia (bottom).
(Picture credit: http://ahdc.vet.cornell.edu/clinpath/modules/heme1/images/platest5.jpg)
- Purchase and organize materials for blood model: Each group gets one spoon and 50 mL tube or cup per person and a bowl/cup of each candy ingredient. Instructors will come around with bottles of corn syrup and monitor pouring.
- If possible, prepare EDTA or Heparin tubes of real blood before and after centrifugation to compare with candy model. If a centrifuge is not available, anti-coagulated blood can be allowed to sit undisturbed in a fridge for a day and a similar pattern will develop. Alternatively download attached picture of centrifuged blood sample to project in class.
- Acquire blood smear from patients through the SEP Resource Center open to all SFUSD public school teachers. We have provided 50 Normal Slides, 25 Patient BT, and 25 Patient AL. These slided present no additional danger than a regular glass slide. The slides were stained with Wright-Giemsa stain and mounted for long term storage. If you don't have access to the Resource center, print pictures of attached patients blood smears instead.
- Prepare handouts and print copies. Word Document and PDF files are provided for each.
- If desired, check out white lab coats from SEP for the second lesson.
Lesson Implementation / Outline
Lesson Day 1:
Assessing preknowledge: What do you know about blood?
- Have class brainstorm on what they know about the functions of blood (e.g. transport of oxygen, nutrients, wastes, and hormones, immune surveillance response to infection, clotting, thermoregulation) and its components (red blood cells, white blood cells, platelets, plasma). Record responses on board.
- Tell students that they have been accepted to med school for the day and that their first class will be on blood.
- Show sample of centrifuged/settled blood in 5 or 10-mL EDTA tube. (if not available show illustration). Tell students that we will try to reproduce what we see with candy. Bottom layer: RBCs, Middle Band: WBCs and PLTs, Top Solution: Plasma
- Start Blood Model:
- Pass out worksheet and introduce activity. Tell students that they are going to make a model of blood using candy to represent the components. RBCs = Red Hots, WBCs = mini marshmallows, PLTs = sprinkles, plasma = corn syrup. Students will be mixing up "blood" in a 50 mL test tube. The goal is to add the appropriate amount of each ingredient to represent the proportion it contributes to the total blood volume (%'s on worksheet).
- Ask materials person from each group to pick up tubes, spoons, and containers of candies.
- Walk students through each layer, how much volume it should take up and what each blood component does.
- Bottom layer: Red Hots in Tube little less than half full - Share info about Red blood cells (RBCs) - most abundant cellular component of blood (40-45% total blood volume), donut shaped without hole, transport gases. RBCs don't have nuclei but are full of hemoglobin which binds oxygen and to a lesser extent, carbon dioxide (most CO2 is transported dissolved in plasma or as bicarbonate). Hemoglobin is specially adapted to bind oxygen in the lungs and release it in tissue capillaries; the reverse is true for carbon dioxide. Hemoglobin gives blood its red color. RBCs are made in bone marrow and circulate for 120 days before being recycled in the spleen or liver.
- Middle Layer - A Couple Marshmallows in Tube - Share info about White blood cells (WBCs) - many types with specialized functions, all involved in immunity and inflammation (0.5% of blood volume). Some WBCs only recognize a specific pathogen. If they find it, they proliferate and secrete products to kill the pathogen or recruit other immune cells to help. Other WBCs can respond to many classes of pathogens and also are involved in clearing debris and repairing tissues following a wound. WBCs are made in bone marrow and circulate in blood. They can also leave blood vessels to patrol tissues or respond to tissue damage or infection.
- Middle Layer - A Few Sprinkles in Tube - Share info about Platelets (PLTs) - fragments of cells that mediate clotting to prevent blood loss (0.5% blood volume). When platelets reach a site of blood vessel damage, they become activated and clump together to form a platelet plug that adheres to the damaged vessel wall to block blood loss. Platelets are formed in bone marrow by giant cells that stick their cytoplasmic extensions into blood vessels, which then break off to make platelets.
- Top Layer - Fill tube with Corn Syrup - Share info about Plasma - the liquid component of blood (55-60% volume), predominantly water. Also contains dissolved nutrients (sugars, amino acids, vitamins, minerals), hormones, antibodies, clotting factors,and large proteins or complexes that act as carriers for substances that don't dissolve in water (fat, hormones, some vitamins). Plasma circulates nutrients throughout the body and picks up waste products for excretion (e.g. urea, carbon dioxide).
- When groups have measured out the dry candies into their tubes, instructors will come around with bottles of corn syrup. Students can then eat their candy blood if desired.
- Collect back materials when groups are done. Have them clean up any spilled corn syrup with damp paper towels.
- Introduction to CBC and Blood Smear: Use take home reading document handout (projected or printed) to present that CBC is used to quantity blood components for each person. Make correlation of the number of people that would be required to represent each component in 1 mL of blood (having a test tube with 1 mL or red food coloring can be useful). Show an image of a blood smear from hand out. Explain how to identify cells in blood smear. Majority of cells are beige/pinkish uniform circles with pale centers; these are RBCs. WBCs are much less frequent but are larger and have nuclei that stain blue/purple. Their shape, size, and nuclear staining pattern varies from cell to cell because there are different types of WBCs. PLTs are distinguishable by their size (much smaller than RBCs).
- Tell students that they are now experts on blood and have graduated med school as hematologists. Hematologists diagnose and treat patients who have disorders of blood. This often causes the composition of blood to be altered or certain cell types to not function properly.
- Test understanding of blood cell functions by asking what would happen if someone didn't have enough RBCs, WBCs, or PLTs or had a defect in their function.
- Tell students that in the next lesson they will be seeing their first patients as hematologists. They will be given some information about their patient and samples of blood to look at and compare with normal blood. Using what they know about the normal function and composition of blood, they will come up with a diagnosis that fits the patient's symptoms and any abnormalities they observe in the patient's blood. Tell students that these patients are relying on them to make the right diagnosis and start them on the appropriate treatment program, so they better be prepared.
- Pass out a handout with more information on blood and blood diseases. Ask students to read it before the next class so they will be ready to diagnose their patients.
Note from Authors to Future Lesson Plan Users: This exact format and amount of content was very successful in a 7th grade class even though it might appear to be an overwhelming amount of information. The take home reading is optional especially if CBC and Blood Smears were covered during Wrap up. Alternatively, a section about blood can be assigned from their textbook.
Lesson Day 2:
- Welcome back hematologists. Warm up question: How do you diagnose a patient with a blood disorder?
- Review concepts learned in lesson 1 (Ask class to name the 4 blood components and give their relative numbers and functions). Helpful to project images in take home reading. Review the basics of CBCs, particularly definitions of Hb (amount of hemoglobin in blood) and Hct (hematocrit; % of blood volume composed of RBCs).
- Introduce activity: Tell students that they first will look at a blood smear and CBC of a healthy person. Then they will receive information about their patient and look at samples of blood and compare it with the normal blood sample. Using what they know about the normal function and composition of blood, their task is to come up with a diagnosis that fits the patient's symptoms and any abnormalities they observe in the patient's blood.
- Ask material-getter from each group to pick up slides of the healthy patient and microscope. Ideally, have miscroscope stations already set up and assign pairs to stations.
- Students first study the CBC and blood smear slides of the healthy/normal patient.
- While students fill in worksheet for normal patient, instructors will visit groups and insure that everybody has properly viewed the slides and understand the CBC values of normal patient.
- As a whole class, discuss findings of the normal patient blood smear. Project image on screen.
- Normal Patient: CBC: values are in normal range. Blood Smear: mostly RBCs, pinkish uniform circles with pale centers, PLT present, WBC rare.
- Introduce patient BT and AL and read out case history to class.
- Assign half of groups to focus on patient BT, other half to focus on patient AL. Have material-getter pick-up the blood smear slides of their assigned patient. (If students finish up with their patient early they can take a look at the other patient)
- Tell students that for the treatment plan portion of the handout, they aren't expected to know drug names, just write down what they think the treatment should accomplish (e.g. getting rid of defective cells, administering normal cells by blood transfusion, etc.)
- Instructors will visit groups and insure that everybody has properly viewed the slides and understand the CBC values of diseased patients
- Give a 5 minute warning for groups to wrap up and prepare to present their findings to the rest of the class. Have them return their slides and microscopes when done.
- As a whole group, students present their observations, diagnosis and recommended treatments.
- Ask the reporters from the groups that focused on BT to present their observations, differential diagnoses, and treatment plans. Discuss any disagreements and appropriateness of diagnoses and treatments.
- Project the patient BT blood smear image and discuss findings.
- Patient BT: RBC values are lower than normal range in CBC. Other values are normal. Blood Smear: mostly RBCs, irregular shape and color, PLTs are present, WBC rare - Consistent with a RBC disorder. Treatment would be blood transfusion.
- For a more advance lesson: This patient has a hemoglobin disorder (Hemoglobinopathy) specifically Beta-Thalassemia major. Both Beta globin genes (major and minor) are defective.
- Ask the reporters from the groups that focused on AL to present their observations, differential diagnoses, and treatment plans. Discuss any disagreements and appropriateness of diagnoses and treatments.
- Project the patient AL blood smear image and discuss findings.
- WBC values above range in CBC, rest of the values are not significantly different. Blood Smear: RBCs are normal, PLT are present, but WBCs are over populated, extremely large. - Consistent with WBC disorder. Treatment would be chemotherapy.
- For a more advanced lesson: This patient has Leukemia specifically Acute Myeloid Leukemia.
- Summarize findings, connecting observations from blood smear and CBC to disease mechanism and patient symptoms. Describe actual treatments for particular diseases if known.
- Ask students what they think caused the diseases in their patients. Have some students share out their ideas. Tell students that some diseases have known environmental or genetic risk factors; others occur randomly or due to unknown reasons. Many blood disorders are largely genetic and are inherited in families (e.g. Sickle Cell Anemia).
Note from Authors to Future Lesson Plan Users: It is at the teacher's discretion if the students needs to define either a RBC or WBC disorder or determine a possible disease. If a disease diagnosis is relevant, then the take-home reading would be useful. In our seventh grade class, the vast majority of the class were able to diagnose the patients with a defect in a specific blood component and provide a relevant treatment option.
Student understanding will be assessed by responses to questions posed to the class, monitoring of group progress during activities, written answers on worksheets/handouts, and oral reports on group findings.
Extensions and Reflections